Luca made $9$ sandwiches for the family picnic. $6$ of them were tuna and the rest were cheese. Complete the number sentences to find how many cheese sandwiches Luca made. $9$ sandwiches in total $- \,6$ tuna $= $
Explanation: $9$ can be separated into two parts: ${6}$ and $?$ We can use subtraction to find the missing part: $9 - {6} = 3$ We can also think about how much more can be added to ${6}$ to get $9$ : ${6} + 3 = 9$ The answer $ 9 - {6} = 3 $ ${6} + 3 = 9$